When working on already laid pipes normally conventional shovel excavators are used in pipeline construction. Working with shovel excavators is particularly disadvantageous when it is a question of laying bare a specific point on underground pipes, e.g. in order to remove pipe breaks, connect branches or to inspect the pipes. As a result of the operation of a shovel excavator it is necessary to remove the soil in a large area and deposit the overburden on the building site. Due to the relatively approximate operation and poor controllability of the shovels, there is a considerable risk of damage to the pipes to be layed bare or those adjacent thereto. In the case of medium-carrying pipes such as gas, water or sewage pipes, this can lead to the escape of the medium and in the case of electric cables to the destruction thereof.
For the planned removing of material so-called suction excavators have been developed, in which with the aid of a fan a vacuum is produced and the material can be suctioned an elephant trunk into a storage tank, where the suction material is separated from the suction air flow, while filtering out dust or other particles contained in the conveying air, before the latter is blown out at the fan outlet side. It has been found that filters in such suction excavators become relatively rapidly blocked by particles entrained in the suction air flow, which impedes or even prevents the suction process.
It is known (EP 368 129 C2) to clean the filters in a continuous manner by supplying water and/or air, but the cleaning capacity obtained is dependent on the nature of the particles entrained in the suction air flow. Particularly in the case of loam or other strongly adhering particles, it is very difficult to keep the filters free over long periods and consequently ensure a relatively long-lasting, trouble-free operation of the suction excavator.